9.1

CVE-2026-39831: Invoking bypass of FIDO/U2F security keys physical interaction in golang.org/x/crypto/ssh

Analyzed
AliasesUBUNTU-CVE-2026-39831DEBIAN-CVE-2026-39831CGA-2226-8qm6-5888
Published 22-05-2026Last modified 22-05-2026

Vulnerability summary

CVE-2026-39831 is a critical (CVSS 9.1) Missing Authorization vulnerability in golang crypto. EPSS estimates a 0.48% chance of exploitation in the next 30 days, higher than 41.3% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 9.1 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
9.1/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.48%
0%100%
Low · -0.01 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 56 · Related 59
OPENSUSE-SU-2026:10842-1OPENSUSE-SU-2026:10845-1OPENSUSE-SU-2026:10856-1OPENSUSE-SU-2026:10949-1OPENSUSE-SU-2026:11053-1OPENSUSE-SU-2026:11126-1

Timeline

  1. 22-05-2026
    PublishedVulnerability first disclosed.
  2. 22-05-2026
    Last modifiedVulnerability information updated.

Description

The Verify() method for FIDO/U2F security key types (sk-ecdsa-sha2-nistp256@openssh.com, sk-ssh-ed25519@openssh.com) did not check the User Presence flag. Signatures generated without physical touch were accepted, allowing unattended use of a hardware security key. To restore the previous behavior, return a "no-touch-required" extension in Permissions.Extensions from PublicKeyCallback.

CVSS metrics

7 scores · 7 sources · 1 version

EPSS trend

Probability

0.48%

Chance of exploitation in the next 30 days

Percentile

41%

Versus all other CVEs

30-day change

Decrease -0.01 pp

From 0.49% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard200 products
  • aactl< 0.4.12-r53
  • act< 0.2.88-r6
  • actions-runner-controllerAll versions (No fix recorded)
  • actions-runner-controller-fipsAll versions (No fix recorded)
  • ageAll versions (No fix recorded)

1 vendor · 200 products · Showing 200 of 2860

References

14 links
Show all 14 references